V Oc Over 1.2 ‍V for Cs2agbibr6 Solar Cells Based on Formamidinium Acetate Additive

Inorganic lead-free Cs 2 AgBiBr 6 double perovskite is a promising material for solving the toxicity and the instability of organic-inorganic hybrid perovskite. However, due to the poor interface contact and inferior perovskite film quality, the open-circuit voltage and the power conversion efficiency of Cs 2 AgBiBr 6 solar cells are directly suppressed. Herein, the film quality of Cs 2 AgBiBr 6 is improved by adding formamidinium acetate‍‍ (FAAc) into the precursor solution. With additive modulation, the grain size of Cs 2 AgBiBr 6 film becomes larger and more uniform. The crystal structure remains unchanged, and the defect density decreases. The photovoltaic performance of the corresponding solar cells are also studied. The average power conversion efficiency of the target device is more than 30% higher than the control device. The best efficiency approaches 2.09%, and the open-circuit voltage is surprisingly high at 1.23‍ ‍V, the highest value reported for Cs 2 AgBiBr 6 solar cells